SIR: I venture to make a few remarks on turret-ships, upon which, as your leading article of yesterday says, the question of naval armaments will turn mainly. I hope you will kindly find room for them, as at this time we should see clearly all sides of the question. I quite agree with you that at present we have no reason to be alarmed by the predictions of Admiral PORTER. You speak of the monitors as only having six 1-inch plates, but from drawings I have, as well as other information, both public and private, I find many of them have 10 and 11 inches of iron -- in some instances they have a solid 5-inch plate over five 1-inch-plates, which is a mode of construction we have not tested, but I have information that from trials at St. Petersburg, it was found that a 5-inch solid plate on five 1-inch plates resisted the impact of shot better than one solid 10-inch plate.

However, the point that should not be lost sight of is the power of these monitors to carry ten inches of armor, for, whether it is made up of one-inch plates or a solid forging, the weight to be carried is the same -- the problem which I hope eventually to solve being water carriage for the heaviest guns and thickest armor in proportion to tonnage.

You mention the monitors only having seven knots' speed, and it might be inferred that turret vessels and speed are not compatible. Our turret ships average ten knots, and it would be as well to see what their armaments are, although let it be remembered that the Royal Sovereign and the Prince Albert were first prepared for smaller but more numerous guns, and that the heavier guns being put into single turrets was a compromise, which did not admit of so efficacious an arrangement as if they had all had double turrets. For instance, the Royal Sovereign has three single turrets and one double one, carrying five guns, weighing in all 564 tons, 18 cwt.; but if she had three double turrets, mounting six guns, there would be a gain of one gun, with 49 tons 14 cwt. less weight, besides the space gained on the lower deck for accommodation, by there being one turret less.

The Prince Albert has the same defect; she has four single turrets mounting four guns, and weighing in all 423 tons, while if she had two double turrets mounting four guns and weighing 303 tons 8 cwt., there would be a saving of 119 tons 2 cwt.

Or she might have two double turrets and one single one, mounting five guns, for the same weight she now has. In both cases the weight would be more central, and give a greater space below for accommodation, beside increasing the weight of broadside, in the case of the Royal Sovereign one-fifth, and the Prince Albert one-fourth.

The Scorpion and Wivern have two double turrets, and although only 1,900 tons, will carry four 300-pounders, the same broadside as the Prince Albert -- of 2,500 tons. I have spoken here of turret vessels with 300-pounders, but if I were to prepare others I would prefer 600-pounders, for we know that Big Will, with only 52 pound charge of powder, at 400 yards, demolished the Bellerophon target. Then a vessel of the Royal Sovereign class would carry four 600-pounders in two double turrets which, if plated with 9-inch iron, would weigh no more than the four turrets and five guns now in her, but giving her a broadside of 2,400 pounds, and what vessel built or to be built could withstand a concentrated broadside from four such guns as these?